Conservation of American Oystercatchers

The American Oystercatcher (Haematopus palliatus) is one of the most conspicuous birds along the Atlantic and Gulf Coasts; the breeding population spans Cape Sable Island, Nova Scotia south to the Yucatan Peninsula and many of the Caribbean Islands. A rangewide survey of winter flocks along the U.S. coasts yielded an estimated population size of 11,000 birds (Brown et al. 2005).

The prevalence of American Oystercatchers was not always the case. In the early 1800s, American Oystercatchers nested on coastal beaches and salt marshes along the entire Atlantic Coast of North America, possibly as far north as Labrador (Audubon 1835, Bent 1929). Specimens document the species breeding in Maine (Forbush 1912, 1925, Bent 1929), but by the early twentieth century, hunting and egging pressure pushed the northern limit of the range south to Virginia where they nested in small numbers (Post and Raynor 1964). After the passage of the Migratory Bird Treaty Act in 1918, oystercatchers began to recover and expanded north. Over the next 80 years (1920-2000), oystercatchers recovered their range along the Atlantic Coast north (Mawhinney et al. 1999).

As American Oystercatchers continued to expand their range and abundance in the northeastern U.S., concurrent evidence suggested that abundance was declining in the core Mid-Atlantic breeding areas (i.e., Virginia, North and South Carolinas). The American Oystercatcher was identified as a Species of High Concern by the U.S. Shorebird Conservation Plan (Brown et al. 2001; https://www.shorebirdplan.org/) and a Focal Species by the U.S. Fish and Wildlife Service-Migratory Bird Program (https://www.fws.gov/birds/management/managed-species/focal-species.php/). Along with the American Oystercatcher Conservation Plan, these management-directed documents identified critical knowledge gaps in the species’ biology that limits effective management, especially in areas in northeastern U.S. where the shorebird has recovered.

Drs. Tom Virzi and Sean Murphy (formerly with Conservation InSight) have their research origins with American Oystercatchers. Dr. Virzi investigated the effects of urban development on the distribution and reproductive performance along coastal New Jersey. Dr. Murphy, just a bit further north, studied the population dynamics in an increasing population in Massachusetts. Both research project established color-banding programs that continue today. With several ongoing oystercatcher banding programs across the species’ range, the American Oystercatcher Working Group provides an online platform to report observations of color-banded oystercatchers (http://amoywg.org/banding-re-sighting/). Once a record is accepted, the reporter will receive detailed information about other locations the bird has been seen.

Due to the growing concern for the viability of oystercatcher populations, the National Fish and Wildlife Foundation (www.nfwf.org) launched a 10-year business plan to help in the conservation and management of the beach-nesting oystercatcher. In 2014, only six years into the program, researchers detected a 10% increase in the American Oystercatcher population. Following the positive findings for the species, the long-term color-banding data was combined for New Jersey, Massachusetts, and South Carolina to explore differences in adult survival, site fidelity, and migratory strategies of oystercatchers (Murphy, Virzi, and Sanders 2017). Our results revealed that South Carolina oystercatchers resided year-round within the state, while Massachusetts oystercatchers were migratory, and the New Jersey population partially migrated with 33% of the breeding population overwintering within the state. Adult survival did not vary among the three state populations. Although the average estimate of adult survival was high (0.89), there was an apparent decline in adult survival (from 0.94 to 0.83) over the study period. Given strong site fidelity (0.91), adult mortality is a critical factor for the viability of local populations and additional studies are required to identify the probable factors affecting adult survival.

Something about future research…We stay involved with ongoing American Oystercatcher research programs along the Atlantic Coast and are hoping to conduct new surveys in coastal New Jersey in the future; currently plans have been put on hold due to the ongoing COVID pandemic. Check back for more information about our new surveys on our website soon. You can also follow us on Facebook to hear about volunteer opportunities to participate in surveys (https://www.facebook.com/conservationinsight/).

To learn more oystercatcher biology, research, and conservation visit the American Oystercatcher Working Group at www.amoywg.org.

References:

Audubon, J.J. 1835. Ornithological Biographies, Vol. 3. Adam and Charles Black, Edinburg, Scotland.
Bent, A.C. 1929. Life histories of North American shore birds. Part 2. U.S. National Museum Bulletin, No. 146.
Brown, S.C. et al. 2001. U.S. Shorebird Conservation Plan. Manomet Ctr. for Conservation Sci., Manomet, MA.
Brown, S.C., et al. 2005. Population size and winter distribution of eastern American Oystercatchers. J. Wildlife Management 69: 1538-1545.
Forbush, E.H. 1912. A history of the gamebirds, wild-fowl, and shore birds of Massachusetts and adjacent states. MA State Board of Ag., Boston, MA.
Forbush, E.H. 1925. Birds of Massachusetts and other New England states. Vol. 1. MA Dept. of Ag. Boston, MA.
Mawhinney, K., B. Allen, and B. Benedict. 1999. Status of the American Oystercatcher, Haematopus palliatus, on the Atlantic Coast. Northeastern Naturalist 6: 177-182.
Murphy, S.P., T. Virzi, and F. Sanders. 2017. Exploring differences in adult survival and site fidelity of migratory and non-migratory American Oystercatcher (Haematopus palliatus) populations. Waterbirds 40: 32-43.
Post, P.W. and G.S. Raynor. 1964. Recent range expansion of the American Oystercatcher into New York. Wilson Bull. 76: 339-346.